Safety lock plug



June 28, 1955 c. A. HUMMA 2,712,118

SAFETY LOCK PLUG Filed Oct. 50, 1951,

wy@ Z3 3 7'* i) OVSH'JS, 7 19 F i 'l 3 INVENTOR CyR/x, HUMMA maz l ,0d/Maan ATTORNEYS United States Patent O SAFETY LOCK PLUG Cyril A. Humma, Reading, Pa. Application October 30, 1951, Serial No. 253,857

2V Claims. (Cl. 339-74) This invention relates to electric connection devices, and more particularly to an improved combination electric plug and socket.

The main object of the invention is to provide a novel and improved electric connection device which is simple in construction, which involves relatively few parts, and which substantially reduces the hazards of short circuits, shocks, broken wiring, and the like, as over plug and socket devices in present use.

A further object of the invention is to provide an improved combination plug and socket assembly which is inexpensive to construct, which is durable, which cannot be disengaged accidentially, which is safer touse than the currently employed devices, and which may be installed readily in any desired location.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure 1 is a front elevational view of an improved combination plug and socket device according to the present invention, shown installed in an appliance and con nected to a conventional plug for connecting the appliance to an electric outlet.

Figure 2 is a top view of the receptacle shown in Figure l.

Figure 3 is a front elevational view, similar to Figure 1, with parts broken away to show details of interior construction and with the plug element thereof detached from the receptacle element.

Figure 4 is a cross sectional view taken on the line 4 4 of Figure 2.

Figure 5 is a cross sectional view taken on the line 5--5 of Figure 2.

Figure 6 is a cross sectional view taken on the line 6--6 of Figure 4.

Figure 7 is a cross sectional view taken on the line 7-7 of Figure 4.

Referring to the drawings, the combination receptacle and plug device is designated generally at 11 and comprises the receptacle portion 12 and the plug portion 13. The receptacle portion 12 comprises a rectangular housing of suitable insulating material having a generally rectangular internal cavity and having the top wall 13', the end walls 14, 14 and the front and rear walls 15 and 16. The end walls 14, 14 merge with respective inwardly extending locking anges 17, 17 at the rim of the receptacle. Designated at 18, 18 are respective metal contact strips secured against the opposing surfaces of respective longitudinally extending grooves 19, 19 formed in the end walls 14, 14, said contact strips 18 having portions 20, 20 engaged against the anges 17, 17 and having offset portions 21, 21 at their opposite ends engaged by ter-Y minal screws 22, 22 threadedly engaged in the opposite ends of the top wall 13. The wires 23, 23 are utilized to connect the terminal screws 22, 22 to the electrical element of the appliance.

Slidably disposed inside the housing 12 is a cover member 24 which is biased downwardly, as viewed in Figures 2,712,118 Patented June Z8, 1955 ice 4- and 5 by a coil spring 25 having its ends seated in respective recesses provided in the cover member 24 and the top wall 13 respectively, as shown in Figure 5.

The plug member 13 comprises a relatively flat main body 26 formed at its side edges with the respective parallel, spaced llanges 27, 27 between which are pivoted the respective opposing arms 28, 28. The pivotal connections of the arms 28, 28 are shown respectively at 29, 29, said pivotal connections being located near the upper ends of the arms 28, 28, as viewed in Figure 5. The arms 2,8, 28 are formed with the locking shoulders 30, 30 at their upper outer portions, as viewed inFigure 5, and said arms are biased away from the lower portion ofthe main body 26 by respective leaf springs 31, 31 secured between the lower portions of the arms 28 and the intermediate portion of main body 26, as shown in Figure 5, the leaf springs 31, 31 being arranged to bias the lower portions of the arms 28, 28 away from the intermediate portion of thepmain body. Secured to the external surfaces of the respective shoulders 30, 30 are the contact elements 32, 32, the top ends of said contact elements being engaged by terminal screws 33, 33 threaded into the top ends of the arms 28, 28.

The intermediate portion of the main body 26 is formed with an axial bore 34 through which the line cord 35 extends, the wires of the line cord being connected respectively to the terminal screws 33, 33.

Normally, when the plug 13 is outpof the receptacle element 12, the cover 24 closes the bottom opening of the receptacle 12, in the manner shown in Figure 3, said cover being provided with the reduced end anges 36, 36 adapted to engage against the lower ends of the contact strips 18, 18 and to allow the main body of the cover to project through the longitudinal aperture defined at the bottom of the receptacle. The spring urges the cover 24 to seating position in said aperture as above explained. The main body 26 of the plug 13 is shaped to t into the above mentioned rectangular aperture in the bottom of the recepatacle element 12, and the shoulder portions 30, of the plug member are adapted to lockingly engage above the flanges 17, 17 in the manner shown in Figures 4 and 5 when the plug is inserted into the receptacle.

^ When the plug is thus inserted the contact elements 32,

32 engage the contact elements 18, 18 and establish electrical connections between the wires of the line cord and the appliance wires 23, 23. The contact elements 32, 32 are biased toward conductive engagement with the contact elements 18, 18 by the leaf springs 31, 31. The plug 13 is also mechanically locked in the receptacle 12 by the biasing action of the springs 31, 31.

When it is desired to disengage the plug 13 from the receptacle 12 it is merely necessary to manually squeeze together the depending lower ends of the arms 28, 28, whereby the plug may be withdrawn from the receptacle by the inward movement of the shoulders 30, 30 toward the intermediate portion of the body 26, whereby said shoulders may be moved past the locking ilanges 17, 17. When the plug 13 is removed from the receptacle 12, the cover element 24 is urged downwardly by the spring 25 into closing position and seals the bottom aperture of the receptacle.

It will be readily apparent that the combination receptacle and plug described above cannot be separated accidentally, and cannot be separated except by manually squeezing together the protruding lower ends of the arms 28, 28. The plug and receptacle therefore cannot be detached accidentally, as by pulling on the line cord 35, shaking the appliance, or in any other unintended manner. It will be further apparent that the plug and socket assembly above described may be employed not only for use with appliances but for permanent house wiring installations, the receptacle members 12 being usable in place ofthepresent-socket receptacles and the plug members 13 being usable in place of the conventionally employed types of present plugs. The receptacle 12 may, of course, be installed in any steel receptacle box or'r'outlet box with complete safety.

While a specific embodiment of an `improved combination receptacle and plug assembly has been disclosed in the foregoing description, it will be understoodthat various ymodifications within the spirit of the invention may 'occur to those skilled in the art.k Therefore, it is intended that no limitations be vplaced on the invention except as dened by the scope of the appended claims.

What is claimed is:

l. In combination, a hollow receptacle, respectivementact members secured in opposite sides of the interior of said receptacle, respective inwardly extending llocking anges'at the rim of the receptacle Vadjacent said contact members, a vplug member having a forward end adapted to enter said'rim, opposed insulated arms pivoted to the sides lof said plug member vadjacent the `forward end thereof, respective contact elements on saidarms arranged to 'engage said contact members when the arms are spread outwaardlyV from the plug member subsequent to insertion of the plug member into the receptacle, spring means biasing said arms outwardly, locking shoulders on said arms arranged to lockingly engage behind said flanges to retain the plug member in the receptacle, a cover'member slidably disposed in said receptacle, and means biasing Said ycover v'member towardengagementV with 'said' flanges, whereby the receptaclev is closed when the plug member 'is withdrawn therefrom.

2. In combination, -a hollow receptacle having agenerally rectangular cavity, respective contact members secured in opposite ends of said cavity, respective inwardly extending locking flanges at the rim of the receptacle adjacent said contact members, a plug member having a forward end adapted to enter said rim and slidably engage in said cavity, opposed insulated arms pivoted to the sides of said plug member adjacent the forward end thereof, respective contact elements on said arms arranged to engage said contact members when the arms are spread outwardly from the plug member subsequent to insertion of the plug member into the receptacle, spring means biasing said arms outwardly, lockingA shoulders on said arms arranged to lockingly engage behind said flanges to retain the plug member in the receptacle, a cover member slidably disposed in said receptacle, and means biasing said cover member toward engagement with said flanges, whereby the receptacle is closed when the plug member is withdrawn therefrom.

References Cited in the le of this patent UNITED STATES PATENTS 797,215 Osborne vet al. Aug. l5, 1905 1,277,071 Hastings et al Aug. 27, 19118 1,890,484 Allenic Dec. 13, 1932 2,102,625 Hubbell, .Tr Dec. 2l, 1937 2,151,226 Ogle Mar. 21., 1939 2,266,130 Theriault Dec. 16, 1941 2,484,525 Norris Oct. 1l', 1949 2,524,701 Grill Oct. 3, 1950 

